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Morphological and genetic characters from cyprinid fishes of the genus Gila were examined to assess a hypothesized hybrid origin of Gila seminuda from the Virgin River, Arizona-Nevada-Utah. The presumed parents, Gia robusta robusta and Gba elegans, are clearly differentiated from one another based on morphology, allozymes, and mtDNA haplotypes. G. seminuda is morphologically intermediate and polymorphic at allozyme loci diagnic for the parental species. Restriction endonuclease analysis of mtDNA showed G. seminuda nearly identical to G. elegans. These

The ubiquitous presence of nonnative fishes, both sport and nongame, within waters of the southwestern United States is the foremost factor preventing immediate conservation and recovery of imperiled native fishes. We present evidence that the two fishery types cannot be co‐managed in sympatry if natives are to persist. A dual responsibility of federal and state fish and wildlife agencies to manage both fishery types creates internal conflicts that typically are resolved in favor of nonnative sport fisheries, despite existence of the Endangered Species Act. We advocate designation of watersheds to be managed exclusively for one fishery type or the other, and implementation of an aggressive program to eliminate nonnatives in native‐designated waters and protect against their reinvasion. To mitigate institutional conflicts, agency infrastructures should be segregated to promote independent management of native fisheries and introduced sport fisheries. This approach can fulfill mandates of both the Endangered Species Act and the 1996 Fish and Wildlife Service policy on recreational fishing.

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